untracked cache: make a wrapper around {open,read,close}dir()
untracked cache: make a wrapper around {open,read,close}dir()

This allows us to feed different info to read_directory_recursive()
based on untracked cache in the next patch.

Helped-by: Ramsay Jones <3e74413778ce9c8bebbbaedfd56741f6850faeaf@ramsay1.demon.co.uk>
Signed-off-by: Nguyễn Thái Ngọc Duy <024f400cd820cb2ddbe54c7fecfd01e45f30bb96@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git